Deno

Use when writing, running, configuring, reviewing, or debugging code in a Deno project, or when scaffolding a new one. Covers dependency management with deno install and deno add, package.json and node_modules support, npm and JSR packages, permissions, where configuration belongs across package.json, tsconfig.json and deno.json, workspaces, the built-in toolchain (fmt, lint, test, check, bench, compile), and publishing.

Use when deploying Deno apps to production, asking about Deno Deploy, or working with `deno deploy` CLI commands. Covers deployment workflows, environment variables, KV database access, custom domains, the --tunnel flag for local development, and the `deno deploy` command reference.

Use when building a web frontend with Deno — running React, Vite, Astro, SvelteKit, Next.js, Nuxt or other npm frameworks under Deno, or working with Fresh, Deno's own island-architecture framework. Covers which path to pick, Fresh 2.x routes, handlers, islands, Preact signals, Tailwind, and Fresh 1.x to 2.x migration.

Use when building features that execute untrusted user code, AI-generated code, or need isolated code execution environments. Covers the @deno/sandbox SDK.

Use when moving a Node.js, npm, Yarn, pnpm, or Bun project to Deno, or when adopting Deno incrementally in an existing JavaScript or TypeScript codebase. Covers using Deno as a drop-in package manager, running existing package.json scripts, CommonJS versus ESM, node_modules layout, lockfile migration, permissions, whether to adopt the built-in toolchain, and per-tool command equivalents.